Smartphone ownership has seen tremendous rate of growth in recent years. One of the fastest growing sectors of smartphone applications is mobile games. In fact, mobile games consistently dominate the list of top applications downloaded in both Android and iOS markets. The popularity of mobile games has led to innovations in both hardware and software, e.g., from the introduction of mobile quad-core CPUs to 3D sensor-based games.
Smartphones offer opportunities for mobile game players to engage in highly interactive, local multi-player game activities, also known as LAN parties. These activities offer high levels of satisfaction and entertainment to the participants, as they allow them to interact with each other on the spot while playing the games. With a traditional gaming platform, such as PCs, gamers have to make a significant effort to setup a LAN game party, e.g., planning the time and arranging a powered table space. In contrast, smartphones are usually carried by the owners, operate on battery, and have small footprints, making them an ideal gaming platform for spontaneous, local multiplayer games.
The strategies used to synchronize game state in multi-player games can be divided in two groups: client-server and peer-to-peer. In the first approach, players synchronize their local game states with the authoritative state held by the server. In the peer-to-peer approach, no single peer is responsible for the game state. Instead, the state is synchronized using a distributed protocol run by all players. The advantages of the client-server model are that it is easier to implement and more resilient to cheating. The appeal of the second approach is that it obviates the need of expensive servers and no node in the network must be present for the duration of the game. There are also efforts to build peer-to-peer based games that are resilient to cheating.
The recent popularity and powerful capabilities of smartphones and mobile devices (including tablets) have enabled development of multiplayer games over wireless networks. Current commercial engines essentially re-use the approaches designed for the wired setup over wireless. Highly interactive multiplayer games, such as FPS, have been implemented both over LAN and wide-area networks (WAN); the latter have much larger network latency. Commercial solutions employ mechanisms that can cope with this large latency over WANs, and simply reuse these mechanisms over the lower latency LANs as well. In the academic community, solutions have been proposed to deal with the high latency of the wireless WAN links and the performance of various broadcasting schemes, such as flooding and distance-based broadcast, has been studied. Multicast has also been proposed to distribute game commands and states, but has not been used in commercial systems.